Preparation

Cook potatoes in large pot of boiling salted water until tender, about 15 minutes. Drain potatoes; cool 30 minutes. Peel potatoes, if desired; cut into 1/3-inch-thick slices. Place potatoes in large bowl. Add chives, parsley, and capers. Combine vinegar, caper liquid, and mustard in small bowl. Whisk in oil. Season dressing to taste with salt and pepper. Pour dressing over potatoes; toss gently. Season salad with salt and pepper. (Can be made 2 hours ahead. Let stand at room temperature.)

Test-kitchen tip:
Test-kitchen tip: Choose potatoes that are all about the same size to ensure even cooking.